Objective: Ischemic preconditioning (IPC) implies that repeated brief episodes of ischemia followed by reperfusion to tissue results in improved tissue survival when its tissue is subsequently subjected to prolonged ischemia. The aim of the present study is to determine if the number of cycles influences the effectiveness of IPC in skeletal muscle ischemia. Materials and Methods: using a total of 41 rat hindlimbs, the hindlimb-reperfusion model was created by temporary cutting both soft-tissue and bony structures, exclusive of femoral vessels, around the thighs, and clamping the vessels with a microvascular clip. The setting of each IPC cycle was determined to be 10 minutes of ischemia followed by 10 minutes of reperfusion. All animals were devided into seven groups: sham controls (SC) group (n=8); the same surgical procedures with no ischemia and no IPC, IR group (n=4); 4-hr global ischemia following no IPC, IPC-1, 2 group (n=7), and IPC-3, 4, 5 (n=5); 4-hr ischemia following 1 cycle
… Moreto 5 cycles of IPC in each IPC group. Each animal was sacrificed after 24-hr reperfusion following the completion of each surgical and clamping procedure, the viability of its anterior tibial muscle was histochemically evaluated using NBT method, and the average necrosis area ratio (%NAR) of each group was caltulated by degitalized computer technique using NIH Image Soft. The %NAR was compared between groups using ANOVA and post hoc test, and each value was expressed as Mean±SEM.. Results: The %NAR of each group was as follows: SC group; 0±0, IR group; 66.2±5.9, IPC-1 group; 27.5±8.0, IPC-2 group; 29.5±6.2, IPC-3 group; 9.6±3.4, IPC-4 group; 10.3±2.2, and IPC-5 group ; 11.4±2.4. The %NARs of all IPC groups were significantly lower than that of IR group (p<0.0001). The %NAR of IPC-3, 4, and 5 were significantly lower, when compared with those of IPC-I and IPC-2 groups (p<0.01). Conclusion: The appropriate cycle number of IPC in skeletal muscle was clarified to be 3 to 5 cycles on the basis of the present study. The future studies are planed to study chemical and pathological evidence on the effectiveness of IPC. Less